Polymerization of olefins, especially ethylene, to form polyolefins is an important commercial process, literally millions of tons of such polymers being produced annually. Among the useful grades of polyethylene is Low Density Polyethylene (LDPE), which is usually made by a high pressure process that yields a polyethylene that has excellent processability, see for instance N Maraschin, Ethylene Polymers, LDPE, in J. I. Kroschwitz, et al., Ed., Encyclopedia of Polymer Science and Technology, H. Mark, 3rd Ed., Vol. 2, Wiley Interscience, (2003) p. 412-441, which is hereby included by reference. Such LDPE usually has short chain branching, and is also believed to have long chain branching (LCB), although the lengths of these long chains is not known. It is believed that the good processability of LDPE is due to the presence of these long chain branches.
There are other grades of polyethylenes that, while not usually having LCBs, are also useful. Although they generally do not process as well as LDPE, they have other superior properties that render them useful. Such grades of polyethylene (PE) include Linear Low Density Polyethylene (LLDPE), which has short chain branches, see for instance D. M. Simpson & G. A. Vaughan, Ethylene Polymers, LLDPE, in J. I. Kroschwitz, et al., Ed., Encyclopedia of Polymer Science and Technology, H. Mark, 3rd Ed., Vol. 2, Wiley Interscience, (2003) p. 441-482 (this reference also has a good comparison and description to the properties of LOPE), which reference is hereby included by reference, and High Density Polyethylene (HDPE), which may be linear or have a small amount of short chain branches, see for instance E. Benham, Ethylene Polymers, LDPE, in J. I. Kroschwitz, et al., Ed., Encyclopedia of Polymer Science and Technology, H. Mark, 3rd Ed., Vol. 2, Wiley Interscience, (2003) p. 382-412, which is hereby included by reference.
It has been a longstanding goal to produce other PEs, such as HDPE or LLDPE, that process similarly to or better than LDPE, while retaining the other superior physical properties possessed by these PEs.
U.S. Pat. No. 6,297,338, which is hereby included by reference, describes a process in which an ethylene copolymerization catalyst is combined with an ethylene oligomerization catalyst that produces α-olefins to produce branched PE similar to LLDPE. No specific mention is made of using an oligomerization catalyst with a high SFC, nor is it stated that the processability of such a polyolefin can be improved by use of such an oligomerization catalyst.
U.S. Pat. No. 6,586,550 describes PEs made by the process of U.S. Pat. No. 6,297,338. The PEs described in this patent were not made using oligomerization catalysts with high SFCs.
U.S. Pat. No. 6,103,946 describes the production of α-olefins using iron complexes of certain diimines of 2,6-diacylpyridines or 2,6-pyridinedicarboxaldehydes. Nothing is said of using the resulting α-olefins in situ to produce a copolymer.
Other references that report simultaneous oligomerization and polymerization of various olefins are World Patent Application 90/15085, U.S. Pat. Nos. 5,753,785, 5,856,610, 5,686,542, 5,137,994, and 5,071,927, C. Denger, et al., Makromol. Chem. Rapid Commun., vol, 12, p. 697-701 (1991), and E. A. Benham, et al., Polymer Engineering and Science, vol. 28, p. 1469-1472 (1988). None of these describe using oligomerization catalysts with high SFCs.